MAP kinase pathway, MAPK

The Mitogen activated Protein kinase pathway or MAP kinase pathway is a key signaling pathway by which cell responds to external stimuli,There are number of such MAP kinase Pathways which involves different proteins each step, but they share some common features.

Generic Pathway

Each MAP kinase Pathway starts with activation of Guanine Nucleotide Exchange Factor or GEF.In this example we see activation of GEF by T cell Adapter protein LAT,which links the ligand binding to the T cell receptor with MAP kinase pathways.

GEF proteins activates small G protein by exchanging GDP bound G protein for GTP.In the GTP bound state the G protein is active and can activate other proteins.

In the MAP kinase pathways the protein activated by small G protein is the MAP Kinase kinase kinase or MAPKKK.

The activated MAPKKK now phosphorylates a second kinase MAP kinase kinase or MAPKK.

MAPKK is a dual function kinase able to phosphorylate both tyrosine and serine on its target

MAPKK phosphorylates and activates third kinase called MAP kinase or MAPK.

Activated MAP kinase now migrates to the nucleus where its able activate transcription factors.